Dome Vents - low

We are often asked how waterproof these are. Well, you wouldn't fit one to the pressure hull of a submarine, but when they are closed, they are effectively waterproof. When open however, they are not, so I wouldn't advise their use on a foredeck, because one day you will forget to close it. Also very useful, when struck with a belay pin or similar, for waking up the crew! The nominal size is the diameter of the hole.